This invention relates generally to vacuum sensors to sense pressure within an enclosed system.
Integrated circuits may be hermetically packaged. There are a number of reasons for hermetically packaging components but, generally, hermetic packaging is used to isolate those components from the deleterious effects of the surrounding environment. Vacuum packaging of integrated circuits in microsystems may enhance device performance and/or to improve reliability.
However, monitoring the pressure within a vacuum package is difficult because stand-alone vacuum sensors typically are too large and costly to integrate within an integrated circuit package. Absent an internal sensor, the internal pressure within the vacuum package cavity is unknown over the life of the product and can only be estimated from gas pressure measured during the packaging process.
Hermetic packaging may also enable control of ambient gas composition and/or pressure. There are techniques to characterize the leak tightness of packages such as fluorocarbon bubble and helium detection tests. However, there are no universal techniques to measure the leak tightness of packages with very small cavities, such as those of a size less than a cubic centimeter, that may be found in numerous commercial microelectromechanical system devices, including those with radio frequency components.
Thus, there is a need for better ways to measure cavity pressure.